1. Field of the Invention
The present invention relates to methods and apparatus in the field of fuel supply systems for internal combustion engines and, more specifically, to systems having components that cooperate to remove contaminants, such as entrained air, from an incoming fuel supply such as diesel fuel.
2. Statement of the Problem
Typical fuel supply systems for diesel engines operate on the principle of a vacuum feed system in which fuel resides within a fuel tank that feeds fuel through a fuel line to a transfer pump or a fuel pump. A fuel filter is most often positioned in the fuel line to remove particles and water from the incoming fuel supply. The fuel line feeds the fuel to an inlet of the transfer pump or fuel pump, which operates to pressurize the fuel for delivery to a fuel injector. Various mechanical and electromechanical linkages exist for fuel delivery, such as distributor-type pumps or electronic control module (ECM) systems that deliver fuel from a common rail system.
Operational deficiencies and inefficiencies of the diesel engine are well known, but commercial implementations of such engines have failed to address known problems. Diesel engines lose power, develop increased exhaust smoke, increased fuel consumption and throttle response symptoms as the fuel filter plugs with use. High-speed diesel engines for use in automotive and marine applications lose torque at higher revolutions. Engine power output is derated for operation at higher altitudes. The industry has simply accepted the fact that such engines operate better on some days than others, and has not sufficiently investigated or corrected the problem, which may be observed by visible changes in the exhaust from a given engine at different times.
The aforementioned problems are commonly perceived to involve timing changes, and the industry has addressed these by the development of xe2x80x9cECMxe2x80x9d technology. Diesel fuel injection systems are primarily hydraulic systems, whether they are mechanically timed or electronically controlled. The injector timing must be precise to a millisecond or engine efficiency suffers. According to the principles of operation for diesel engines, the injectors are timed to deliver fuel to a compressed air body that resides within a piston-cylinder assembly as the piston rises towards top dead center (TDC), i.e., the top of the stroke. The heat created by pressure is sufficient to cause ignition of the fuel as it combines with oxygen in the air. The injector pulse ideally delivers a spray of fuel at an instantaneous point in time, but the reality is that the spray persists for only an instant, e.g., about five milliseconds or less at idle. Thus, engine performance is optimized for initialization of the injector timing at a point in time prior to when the piston reaches TDC. Combustion byproducts, such as nitrous oxide and particulates, are reduced by this optimization. Additional features of optimized engine performance include an optimized conical spray pattern geometry and a spray of minimum duration. Entrained air on the pressurized side of the diesel injector pump disrupts the spray pattern, retards the injection timing, and on xe2x80x98ECMxe2x80x99 controlled engines, increases the duration of the injection, all of which reduces the available power from the engine and result in incomplete fuel combustion.
U.S. Pat. Nos. 5,746,184 and 5,355,860 to Ekstam both address fuel delivery systems for diesel engines, and are hereby incorporated by reference to the same extent as though fully disclosed herein. These patents provide a significant advance in the art by demonstrating that diesel engine performance can be enhanced through the use of an air-fuel separation system that removes entrained air from the fuel. These systems are now sold commercially under the trademark FUEL PREPARATOR(copyright) as retrofit devices for diesel engines and consistently provide significant improvements to fuel economy together with reduced particulate matter, carbon monoxide, and NOX emissions. According to U.S. Pat. No. 5,746,184, fuel is fed to the filter under a positive pressure where the filter has pore openings sized smaller than 25 microns and, preferably, of about 15 microns.
The vacuum feed concept of fuel pump intake systems has lead to commercial implementations of fuel transfer and injector pumps having vacuum and cavitation problems that add vapor phases of air and flashed fuel vapor to the fuel. It has been documented that the air which is usually dissolved in a fuel is pulled out of solution at the inlet side of these pumps due to suction at the intake. A greater vacuum pressure or suction is associated with increased chances of cavitation that further increases the amount of vapor that is entrained in the fuel. U.S. Pat. No. 5,539,214 to Ekstam, which is hereby incorporated by reference to the same extent as though fully disclosed herein, teaches the use of a fuel-fed double seal assembly providing improved isolation of intake and outlet sides of a fuel pump.
Various regulatory agencies including federal, state and municipal governments are studying the environmental problems associated with diesel emissions. The primary problems are that diesels emit a relatively disproportionate share of NOX and particulate emissions, which result in an unsightly brown cloud. The particulates are increasingly suspected or implicated as a cause of respiratory problems. Various regulatory schemes have been proposed or implemented to address these problems. There is a real and growing danger that diesel engines, as they are presently constructed, will be unable to meet future emissions requirements without substantial changes to diesel fuels and the use of particulate traps. Although the currently manufactured and commercially marketed model of U.S. Pat. Nos. 5,355,860 and 5,746,184, work well, filter design and size relationship to the device could cause models with greater volume and flow capacity to become quite large and bulky.
The present invention overcomes the problems that are outlined above by providing further enhancements to fuel delivery systems and methods. In combination and as individual components, these enhancements result in improved fuel economy and reduced emissions across a wide variety of diesel engine applications.
One aspect of the fuel delivery system described herein is to provide improvements to prior air-fuel separation systems.
For example, an electronic heating element that is integrally formed with the air-fuel separation system may be used to heat fuel for preconditioning prior to air-fuel separation, i.e., the heating element may be disposed upstream in a flow pathway with respect to the air-fuel separation system. The electronic heating element may be operably configured to receive electricity from a source external to a vehicle on which the air-fuel separation system is installed, or it may be adapted internally to receive electricity from an on-board electrical generator or alternator.
Another such aspect involves the use of check valves having a coil spring and a valve member, wherein the valve member has a shaft received within the coil spring and a semispherical head connected to the shaft. This assembly may be provided as a retrofit assembly to existing systems, such as the aforementioned FUEL PREPORATOR(copyright), to prevent or remediate failure of prior spring and ball valves due to groove wear under conditions of long-standing use.
Another such aspect involves the water separator. To operate properly the device must have an unrestricted flow of fuel that is relatively free of water and foreign objects that could render the transfer pump inoperative. Water separators can be made of many different materials such as cellulose, microglass, wire or synthetic screen or combinations thereof. Many fuel filters are marketed as combination fuel filter-water separators. Many of these products plug quickly with use and restrict fuel flow. Should any of these products find their way into use on an air separator device, they could cause operational failures of the air-separation device. The water separator must not create restriction of fuel flow to the device, therefore, the design is most important. The material best suited for the element of the water separator is screen, either wire or synthetic. The pore opening of the water separator screen could be from 30 microns to 144 microns. However, 70 to 100 microns is preferred. The screen is pleated to increase surface area of the water separator. The surface area of the stripper screen should be sufficient to reduce the flow/pressure of the fuel so as not to force any water through the screen with normal use. This assembly may be provided as a retrofit assembly to existing systems, such as the aforementioned FUEL PREPORATOR(copyright).
Another such aspect involves the fuel filter. The conventional design concept for spin-on fuel filters commonly used by and available to the consumer addresses the removal of the accepted contaminates, liquids and particulates, normally thought to be in the diesel fuel. This concept dictates the pore rating of the filter media, and void volume or capacity of the filter media. Also, the clearances and passages within the filter are only adequate for the flow considerations i.e., single phase or one directional flow, affecting restriction to be within operating constraints of the application equipment. As described herein, improvements to these conventional filters are provided because it is now recognized that additional performance demands are imposed when filters are used for air separation and removal. Therefore, the design of the conventional filters are modified to better enable them to meet the performance demands involving the process of air-vapor separation from liquids, such as diesel fuel or other petroleum based liquids.
It is well known that petroleum based liquids can contain large volumes of entrained air. These volumes of air-vapor that become entrained in diesel fuel or that develop within the system can greatly exceed the ability of the filter to contain or store the air-vapors until the filter is changed as is the case with particulate contaminates. The separation and removal of air-vapor is a continuous process. The entrained air/vapor is separated by the phenomena of the wetted porous paper resistance to air or vapor passage. The magnitude of resistance to vapor passage is dictated by filter element pore size and film strength or surface tension of the liquid. The removal of the separated air/vapor from the filter occurs through floatation facilitated by filter design and predetermined flow pathways created in the filter head. The filter design for this process must consider a bi-directional flow, as liquids are passing in the normal direction while air vapor or bubbles are rising in opposition to or attempting to xe2x80x9cfloat againstxe2x80x9d the incoming flow of liquid. The clearances between the filter element and the inner wall of the filter must be great enough to allow the flow velocity of the liquid to be reduced to a level well below that of the flotation rate of the bubbles. The top plate of the filter should be formed so as to place the fuel ports in the upper most or raised position in the plate. This will improve the pathway of the bubbles rising to the top of the filter assembly for discharge through the air bleed port. Therefore, the improved design for air-separation or filter cartridges, where the air-fuel separation cartridge has a filter, an external wall and a plenum between the filter and the external wall comprises of the air-fuel separation cartridge having a predetermined design according to the relationship
(V/CR) less than F*D/RR,xe2x80x83xe2x80x83(1) 
where V is the volume of the plenum, CR is the peak consumption of throughput rate of fuel, F is a residence factor of at least one, D is the bubble rise distance equal to the height of filter cartridge, and RR is the bubble rise rate. F is more preferably at least two, and most preferably at least three.
Although the cylindrical shape can be utilized with effect if the formula (V/CR) less than F*D/RR, is followed, a xe2x80x9cconicalxe2x80x9d filter design is preferred. A frustroconical filter design is especially preferred. The cone shape, with the smaller diameter at the top, results in an increased clearance in the upper portion of the filter thus reducing the fuel flow velocity. Preferred embodiments also obey equation (1) for bubble rise rates in the context of all points along the plenum cross section. As the fuel migrates to the lower area of the filter, the filter element diameter becomes larger. The total flow rate, however, does not increase. The throughput flow of the fuel passing through the filter element reduces the velocity. Additionally, the filter most preferably has a nominal filtration diameter ranging from 1 micron to 10 microns which, in contrast to conventional filters, is a broader range of diameters permitted by the conical geometry. The filter is preferably formed as a ribbed conical cylinder having two layers comprising an outer layer of fibrous material and an inner layer of cellulose. The fibrous material is preferably compressed microglass, and filters of this construction demonstrate an improved service life.
Another improvement of the fuel delivery system includes a dividing partition protruding from the base of the filter head into the area of the filter or cavity formed when the filter is attached to the filter head. This partition or wall, protruding from the base of the filter head to the top plate of the filter and extending to the interior wall of the filter, would effectively separate the area between the filter head and the filter top plate into two separate chambers, isolating the ports used for exhausting the unwanted gasses from the incoming flow of liquid and establishing a separate discharge pathway for the unwanted gasses. What was once a common area of turbulence and eddies created by the incoming flow of liquid, is now two separate chambers, an inlet chamber for incoming fluid and an outlet chamber for the collection and discharge of unwanted gasses. The proper positioning of the dividing partition permits communication through a number of ports in the top plate that allow unrestricted flow of the incoming liquid into the filter, while other ports leave sufficient openings for the passage of bubbles to rise into the newly created outlet chamber and be discharged through the air bleed port.
Another improvement involves the area of the filter head surrounding the air bleed port. An air bleed port is formed as a simple hole machined into the filter head. The improvement would consist of forming an inverted cup in the filter head in the area surrounding the air bleed port. The inverted cup should be of sufficient size and shape to aid in the collection and channeling of the bubbles to the air bleed port for discharge.
Yet another aspect includes a non-spilling filter assembly for filtration of fluids. The filter assembly comprises a filter head including an inlet for receiving the fluids to be filtered, an outlet for the fluids to exit the filter head after the fluids have been filtered, a threaded connector for use in coupling the filter head with a filter cartridge when a filter cartridge is attached to the filter head, and a plug of a predetermined volume sufficient to accommodate drainage of the fluids from the filter assembly. A filter cartridge may be threadably attached to the threaded connector. The filter cartridge includes an external wall providing a reservoir volume sufficient to accommodate the plug such that the reservoir is able to contain the predetermined volume of the drainage fluids when the filter cartridge is detached from the threaded connector and the plug is withdrawn from the reservoir. A cap is provided for selective use in sealing the reservoir to retain the predetermined volume of fluid drainage with the reservoir when the filter cartridge is detached from the threaded connector. An optional air-bleed port extends from at least one of the inlet and the outlet in position to facilitate drainage from the non-spilling filter assembly. This air-bleed port has a first end in fluidic communication with a second end, the first end being in fluidic communication with the corresponding one of the inlet and the outlet, and the second end being positioned for sealing engagement with respect to an interior confines of a filter cartridge when the filter cartridge is attached to the threaded connector, such that removal of the filter cartridge from the threaded connector permits the fluidic communication between the first end and the second end to break hydraulic vacuum and facilitate drainage from the corresponding one of the inlet and the outlet.
The non-spill filter assembly may be used by flowing fluid for filtration on a flow pathway between the inlet and the outlet, selectively detaching the filter cartridge from the threaded connector to withdraw the plug from the reservoir, and draining fluids from the inlet and the outlet into the reservoir. The cap may be used to seal the fluids within the reservoir by installing the cap to cover the reservoir. The cap, by way of example, may include a threaded nipple and the sealing of fluids in the reservoir may be accomplished by threading the threaded nipple of the cap into the threaded coupling of the filter cartridge.
The air-fuel filter and the water separator are functioning components of the fuel delivery system. Spin-on fuel filters and water separator filters of various size, design, and materials have become abundantly available. With the availability of xe2x80x9cwill fitxe2x80x9d filters of unknown qualities that could be interchanged, it is impossible to assure high levels of performance. Therefore, it is of great importance that usage of the proper air-fuel filter and the water separator on the present invention be controlled. The ability of the xe2x80x9cunique and usefulxe2x80x9d feature of the non-spill filter, when property used not only eliminates contamination of the environment, but also prevents the use of xe2x80x9cwill fitxe2x80x9d filters on the invention that could negate the important functions of the device.
Another aspect involves the addition of a screen type sock filter on the end of the pickup tube that delivers the fuel from the interior of the filter. This tube extends to the bottom of the filter. The fuel in this area of the filter is more apt to be free of any air-vapor that could have passed through the filter. To further reduce the chance of random bubbles entering the pickup tube and passing on to the engine, the improvement features a wire screen filter or xe2x80x9csockxe2x80x9d surrounding the open end of the pickup tube. The screen filter or xe2x80x9csockxe2x80x9d is constructed as large as possible yet small enough to fit through the opening in the top of the filter where it attaches to the nipple. The filter xe2x80x9csockxe2x80x9d could be constructed of similar screen as used in the water separator. The xe2x80x9csockxe2x80x9d forms a barrier to bubbles coming close to the high flow area surrounding the tip of the pickup tube.
Additional details, object, and advantages concerning the aforementioned aspects of the invention will be apparent to those skilled in the art upon reading the following text together with the accompanying drawings.